: Our remarkable capacity to process information in sound is demonstrated everyday as we make sense of the continuous pattern of variation in the acoustic signals we encounter. The purpose of the proposed research is to better understand this ability in normal-hearing adults through controlled measured of their ability to detect and discriminate variation in acoustic patterns made up of tones. There are three keys elements of our approach. First, all efforts are linked by a single theoretical frame work where the information in the patterns is given precise meaning and listener performance is evaluated relative t a common performance standard. Second, the extent to which listeners make use of (weight) different sources of information is determined from trial-by trial analyses of the data. Third, specific hypotheses regarding the outcome of proposed experiments are generated based on known signal transformations performed by the cochlea and decision model that has make accurate prediction for the results of many past studies [R.A. Lutfi, J. Acoust. Soc. Am, 748-758 (1993)]. These three elements are combined to achieve five specific aims. Aims 1-3 are to understand how variation in pattern components along one acoustic dimension interferes with detection of a change in another, how pattern components combine to mask a single tone, and how tone detection is influenced by covariation among of pattern components. Aim 4 and 5 to assess the listener's ability to detect convariation among pattern components, and detect lawful covariation of tone partials in the identification of a real resonant resource. The proposed studies will further our understanding of how natural redundancies in everyday sounds aid detection in noisy backgrounds, and how listeners process invariant relations among spectral components that define properties of speech and other meaningful sounds. The significance of the mission of the NIDCD us that the results for4m normal-hearing adults will allow us to better evaluate real or presumed auditory information processing deficits of young children, the elderly, and individuals with hearing loss.